1DTU Space – National Space Institute, Technical University of Denmark, Department of Geodesy, Kgs. Lyngby, Denmark
2Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
3Department of Geography, College of Science, Swansea University, Swansea, UK
4Geophysical Institute, University of Alaska, Fairbanks, USA
5Geological Survey of Denmark and Greenland, Copenhagen, Denmark
6Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, the Netherlands
7Faculté des Sciences, de la Technologie et de la Communication, University of Luxembourg, Luxembourg
8Centre for Ice and Climate, University of Copenhagen, Copenhagen, Denmark
Received: 23 Jan 2014 – Discussion started: 21 Feb 2014
Abstract. Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance on the decadal scale. To improve the projection of future sea level rise, a long-term data record that reveals the mass balance beyond such episodic events is required. Here, we extend the observational record of marginal thinning of Helheim and Kangerdlugssuaq glaciers from 10 to more than 80 years. We show that, although the frontal portion of Helheim Glacier thinned by more than 100 m between 2003 and 2006, it thickened by more than 50 m during the previous two decades. In contrast, Kangerdlugssuaq Glacier underwent minor thinning of 40–50 m from 1981 to 1998 and major thinning of more than 100 m after 2003. Extending the record back to the end of the Little Ice Age (prior to 1930) shows no thinning of Helheim Glacier from its maximum extent during the Little Ice Age to 1981, while Kangerdlugssuaq Glacier underwent substantial thinning of 230 to 265 m. Comparison of sub-surface water temperature anomalies and variations in air temperature to records of thickness and velocity change suggest that both glaciers are highly sensitive to short-term atmospheric and ocean forcing, and respond very quickly to small fluctuations. On century timescales, however, multiple external parameters (e.g. outlet glacier shape) may dominate the mass change. These findings suggest that special care must be taken in the projection of future dynamic ice loss.
Revised: 28 Jun 2014 – Accepted: 13 Jul 2014 – Published: 18 Aug 2014
Khan, S. A., Kjeldsen, K. K., Kjær, K. H., Bevan, S., Luckman, A., Aschwanden, A., Bjørk, A. A., Korsgaard, N. J., Box, J. E., van den Broeke, M., van Dam, T. M., and Fitzner, A.: Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age, The Cryosphere, 8, 1497-1507, doi:10.5194/tc-8-1497-2014, 2014.